Virtual Labs

1. Which statement about the structure of a BJT is correct?

a: The emitter is lightly doped and wide Explanation

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b: The base is heavily doped and thick Explanation

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c: The collector is moderately doped and larger in size Explanation

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d: The base and collector have identical doping levels Explanation

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2. In an NPN transistor, which current is typically the largest?

a: Base current I_B Explanation

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b: Collector current I_C Explanation

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c: Emitter current I_E Explanation

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d: I_B and I_C are always equal Explanation

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3. Which parameter defines the efficiency of carrier injection from the emitter into the base in a BJT?

a: Emitter injection efficiency (γ) Explanation

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b: Early voltage (V_A) Explanation

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c: Base transport factor Explanation

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d: Thermal voltage Explanation

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4. For a PNP transistor in forward-active mode, which biasing condition is correct?

a: Emitter-base forward-biased, collector-base reverse-biased Explanation

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b: Both emitter-base and collector-base reverse-biased Explanation

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c: Emitter-base reverse-biased, collector-base forward-biased Explanation

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d: Both emitter-base and collector-base forward-biased Explanation

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5. A BJT has β = 150. If I_B = 40 μA, find I_C.

a: 4.5 mA Explanation

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b: 6.0 mA Explanation

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c: 8.0 mA Explanation

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d: 12.0 mA Explanation

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6. When a BJT operates in cutoff mode, what is the approximate collector current I_C?

a: Close to β × I_B Explanation

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b: Zero or nearly zero Explanation

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c: Equal to I_E Explanation

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d: Maximum possible Explanation

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7. In a BJT, how does the Early effect influence the collector current I_C?

a: IC decreases as V_CE increases Explanation

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b: IC remains constant regardless of V_CE Explanation

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c: IC slightly increases due to base-width modulation Explanation

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d: IC abruptly drops to zero at high V_CE Explanation

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8. A BJT amplifier has β = 200 and a base current I_B = 50 μA. If the Early voltage V_A = 80 V and V_CE = 10 V, estimate I_C considering the Early effect.

a: 9.5 mA Explanation

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b: 10.0 mA Explanation

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c: 11.0 mA Explanation

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d: 12.5 mA Explanation

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9. In a BJT, when the base is extremely thin and lightly doped, which phenomenon becomes more significant?

a: Emitter crowding Explanation

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b: Base-width modulation and collector current enhancement Explanation

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c: Thermal runaway Explanation

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d: Avalanche breakdown Explanation

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Bipolar Junction Transistors